Semiconductor transistors, in particular field-effect controlled switching devices such as a MISFET (Metal Insulator Semiconductor Field Effect Transistor), in the following also referred to as MOSFET (Metal Oxide Semiconductor Field Effect Transistor) and a HEMT (High Electron Mobility Field Effect Transistor) have been used for various applications including but not limited to use as switches in power supplies and power converters, electric cars, air-conditioners, and in consumer electronics, for example stereo systems and communication technology.
In recent years, HEMTs have found wider use in low loss high frequency and low loss high power applications. In particular, Gallium nitride (GaN) based HEMT-devices have been found to be well suited for use in DC rectifiers, power microwave and radar amplifiers, low noise amplifiers, and high temperature elements, etc. Gallium nitride (GaN) material shows a high polarization effect, including spontaneous polarization and piezoelectric polarization. Even without being doped, this polarization effect allows forming a two-dimensional-electron gas (2DEG) adjacent to an interface (heterojunction) of a GaN/AlGaN (gallium nitride/aluminum gallium nitride) heterojunction structure (or GaN/AlInGaN, AlGaN/AlInGaN, aluminum indium gallium nitride). In a 2DEG, the electron concentration is related to the intensity of polarization. 2DEG sheet electron concentration of GaN/AlGaN heterojunction structures can reach very high values. Therefore, field-effect-transistors based on GaN/AlGaN heterojunction structures are able to control very large current.
Often different functions are desired to be integrated in a single device or integrated circuit (IC) to minimize cost, size and weight of the electronics. However, existing concepts for combining GaN based HEMTs with widely used silicon based devices, for example silicon based CMOS (Complementary Metal Oxide Semiconductor) devices, result in high manufacturing costs.
Accordingly, there is a need to provide cost-effective methods for forming integrated semiconductor devices in GaN-on-silicon technology.